This invention relates to a product for adsorbing water vapor from ambient air, and more particularly concerns a device which confines granules of a substance capable of absorbing and desorbing water vapor.
A number of granular solid water-insoluble inorganic desiccant materials are generally available which can reversibly adsorb moisture vapor from air or other gas mixtures while retaining their granular form. Such materials include for example, calcium sulfate, zeolites (e.g. Linde molecular sieves 4A), alumina, magnesia, and silica gel. In their usual manner of use, the granular materials are disposed in columns through which a gas is passed, or disposed in thin layers in horizontally oriented trays which contact the gas to be treated. When the absorbent material becomes fully saturated with water, its absorbing capacity can be restored by heat treatment at temperatures in the range of 100 to 200 degrees centrigrade which drives off the absorbed water. The degree of saturation of the granules can in certain instances be monitored by the addition of trace amounts of visibly distinctive indicator substances. When the indicator substance is a thermally stable, inorganic cobalt compound, the dry form generally has a blue color and the wet form generally has a pink color. The transition to the wet color preferably occurs after saturation of the desiccant with water.
The use of silica gel granules confined within porous containers is well known for maintaining the dryness of sealed enclosures containing equipment or substances sensitive to moisture. Such porous containers are generally cellulosic paper pouches which, although capable of a limited amount of regeneration treatment, do not permit visual observation of the granules. The paper pouches, because of their limited strength and thermal resistance, are restricted to use in small sizes and in service conditions which do not require repeatd regeneration or long term durability to rough handling.
It is accordingly an object of the present invention to provide a dehumidifier device which utilizes desiccant granules containing a visibly distinctive indicator substance.
It is another object of this invention to provide a device as in the foregoing object wherein said desiccant granules possess a large water-holding capacity and have sufficient cohesive strength to resist physical degradation with repeated thermal treatment.
It is a further object of the present invention to provide a device of the aforesaid nature wherein the desiccant granules are confined within a porous container capable of withstanding repeated thermal regeneration of the granules.
It is another object of the present invention to provide a device of the aforesaid nature wherein the confined granules are visibly discernible.
It is a still further object of this invention to provide a device of the aforesaid nature of sturdy and durable construction amenable to low cost manufacture.
These objects and other objects and advantages of the invention will be apparent from the following description.